Inline characterizations of finFETs are extremely challenging given the increasingly small dimensions of finFETs. Electrical characterizations are most relevant to final performance of finFETs. Existing technology, such as standard inline characterizations with optical or X-ray illuminations are challenged since the dimensions of finFETs are becoming very small fractions of the illumination wavelengths. Critical dimension atomic force microscopy (CD-AFM) measurements can only scan small regions of one (or a few) finFETs, and can only provide topographical information of the finFETs. Critical dimension scanning electron microscope (CD-SEM) measurements have limited precision and can only provide dimensional information. Further, transmission electron microscopy (TEM) is destructive to the finFET and can only provide a very limited area of electrical characterization. Ellipsometry and scatterometry are limited by the very small fraction of device sizes to the irradiation wavelengths. X-ray systems are challenged by the increasingly small amount of material for interaction with the X-rays.
A need therefore exists for methodology enabling precise inline characterization of small finFETs without destruction of the finFETs, as early in the manufacturing process as possible.